This invention relates generally to a gear rattle detector. More particularly it is directed to a gear rattle detector including a magnetic pick-up which detects gear rattle by sensing a break in the magnetic flux path across meshing teeth of a ferrous gear set if the teeth momentarily move out of meshing contact. The gear rattle detector is adapted for use in an automotive transmission having a plurality of gear sets. It is also adapted for use in a laboratory instrument.
A typical gear set includes drive and driven gears having teeth which move into and out of meshing contact as the gears rotate. A tooth on the drive gear moves into contact with a corresponding tooth on the driven gear as the two teeth mesh. In the ideal case, this contact is maintained as the gears rotate from the point of initial contact to the point of final contact, after which continued rotation moves the two corresponding teeth out of mesh. At this time two other corresponding teeth have moved into mesh. Thus at all times there should be contact between corresponding teeth.
As a practical matter, gear teeth must have some backlash and clearance in order that they may be moved into and out of mesh smoothly. Manufacturing tolerances and vibrations in the driveline may cause accelerations and decelerations which may result in momentary separation of the meshing teeth. These conditions normally give rise to some slight gear rattle which generally is acceptable. However, where gear rattle is excessive, noise often becomes objectionable.
In an automotive transmission, for example, several constantly meshed gear sets may be employed. Where objectionable gear rattle is encountered, it often is difficult to isolate the particular gear set causing the problem.
There is a need for a simple gear rattle detector which can determine which gear set develops objectionable rattle and under what operating conditions it is developed. The gear rattle detector should be simple, inexpensive, easy to construct and rugged enough to be incorporated within the transmission itself. It also should be amenable to use in a laboratory instrument.